This invention relates to the preparation of samples of blood plasma and blood serum for analysis. It will be appreciated that if blood cells are separated from a whole blood sample the supernatent will comprise plasma if a suitable anticoagulant is present or serum if clotting is allowed to occur. This invention is equally applicable to samples of plasma or serum though for convenience the invention is described throughout in terms of blood plasma samples.
In a typical hospital procedure, a sample of blood is taken from a donor patient on the ward and is placed in a blood sample tube. The tube is then sealed and labelled with the name of the donor, the date and time and any such other data relevant to the identity of the blood sample that is required. The sealed sample tube is transported to the laboratory where a technician copies the information on the sample tube label to an empty plasma sample tube. The blood sample tube is then centrifuged to separate the plasma constituent of the blood from the blood cells and the plasma transferred to the labelled plasma sample tube either by pipette or simply by pouring if an amount of special plastic beads has been added to the blood sample prior to centrifuging so that on centrifuging a barrier is formed between the plasma and the blood cells. Both sample tubes are then sealed with screw caps, the blood sample tube being discarded to avoid contamination and the labelled plasma tube retained for subsequent analysis.
This procedure involves certain steps at which errors may occasionally occur unless the technician exercises extreme care. Thus, for example, the technician is required to copy the data from the blood sample tube onto the label for the plasma sample tube; almost inevitably mistakes will be made from time to time. In addition, the normal procedure invites the technician to label a batch of, say, sixteen plasma sample tubes with data corresponding respectively with sixteen blood sample tubes which have been sent from the ward. After centrifuging, the plasma from each blood sample tube has to be transferred to the appropriate plasma sample tube; the risk of plasma being transferred into a wrongly labelled sample tube is self evident.